''Collapse onto scattering centre'' in quasipotential theory

Quasipotential equation for the wave function in the impulse representation is investigated for the case of singular attractive potential U(r)=-lambda r-2. It is shown, that discrete energy spectrum in the nonrelativistic limit do not depend on an arbitrary constant and there appears no collapse onto scattering centre. These results are a consequence of self-adjointness of quasipotential operator in the impulse representation (''deficiency-index'' n=0) in the comparison with Lippmann-Schwinger operator (''deficiency-index'' n=1)